Jerry Lodriguss

Jerry Lodriguss has been a professional photographer for more than 35 years specializing in sports and astronomical photography. For 20 years he was the staff sports photographer for the Philadelphia Inquirer newspaper. Today he is an author, photographer, publisher and educator writing and teaching about astrophotography.

Astrophotography Techniques with the Canon EOS System

August 14, 2012

Astrophotography is the imaging of celestial objects such as the Sun, Moon, planets, comets, stars, clusters, nebulae and galaxies. Astrophotography captures the beauty and majesty of the night sky and wonders of the universe.

Canon DSLRs are amazingly versatile for astrophotography. We can shoot long exposures of deep-sky objects at high ISOs because Canon CMOS sensors are remarkably sensitive and have exceptionally low noise. We can also use them to do time-lapse photography of the heavens, and even use the high-definition video modes for high-resolution planetary photography. Unlike specialized astronomical CCD cameras, DSLRs don't require a computer for use in the field for focusing and recording of the images.

We can get started in astrophotography with really simple equipment – just a camera and lens on a tripod. We can take shots of constellations and asterisms like the Big and Little Dippers and Iridium Satellite flares. From a dark-sky location, we can even shoot the Milky Way – our own galaxy as we see it from inside.

With longer focal lengths on an equatorial tracking mount, we can piggyback a 50mm lens with a ball-and-socket head on top of a telescope and shoot large areas of star clouds and dark nebulae. Lenses with longer focal lengths, such as Canon's 200mm f/2.8 L USM L, can be used to shoot close-ups of deep-sky objects such as the fascinating Antares-Rho Ophiuchi complex.

Celestial objects, from our perspective down here on Earth, can range in size from gigantic – such as the Milky Way stretching 180 degrees from horizon to horizon – to extremely small, such as galaxies and planets which require thousands of millimeters of focal length to shoot. Astronomical subjects also come in all shapes, sizes and brightness. Some can be shot with exposures of just a couple of minutes, but others require hours of total exposure. For smaller objects we will need longer focal lengths such as with the shots of M13, the Great Globular Cluster in Hercules, and M20, The Trifid Nebula in Sagittarius, which were shot with a telescope with 1,000mm of focal length on an equatorial mount. Saturn, was shot with 5,600mm of focal length and 400 stacked video frame grabs from the EOS 60D's High-Definition video mode.

Special Considerations for Deep-Sky Astrophotograph

Image Trailing

Celestial objects in the sky all appear to move because of the Earth's rotation. This is why the Sun seems to rise in the east, move across the sky during the day, and set in the west. It is not because the Sun is moving, it is because the Earth is spinning on its axis like a top, taking about 24 hours to make one complete rotation.

Because many objects in the sky, such as nebulae and galaxies, are faint, they require long exposures. This becomes a problem when shooting on a fixed tripod. Even the stars will trail during a long time exposure. How much they will trail will depend on the length of the exposure, the focal length of the lens, and the location of the object in the sky. You will get more trailing with longer exposures, and longer focal lengths, and with objects in the sky near the celestial equator.

For longer exposures without trailing, and at longer focal lengths for smaller objects, you will need a special equatorial mount to track the sky and objects as they move to compensate for the Earth's rotation. At focal lengths longer than about 500mm for long exposures you will also need to guide, which requires a separate computerized CCD guiding camera.

The Darkness of the Night Sky

The darkness, or brightness, of the night sky at your observing location will have a tremendous impact on the quality of your images. Nights when a bright Moon is up can also adversely impact astrophotography of faint deep-sky objects.

From downtown in a light-polluted city, you will only be able to see the brightest stars and planets in the night sky, and you will have a very hard time photographing anything faint.

As with other forms of nature photography, you really have to go to where the subjects are best seen. In the case of astrophotography of the night sky, this usually means a truly dark location, far away from the light pollution found in cities and suburbs, if you want to shoot faint deeps-sky objects.

For those that can't travel far enough away to find those ideal conditions, there are some special filters that will help by filtering out some of the light pollution, such as Astronomik CLS filter. Using these filters from a dark-sky site will help even more, because they also filter out natural airglow, which is present in the atmosphere, everywhere, all the time. These filters allow longer exposures and increase the contrast between the object and sky background and make them more visible.

White Balance

Shooting daylight white balance will almost always produce an ugly red-brown sky background. Unfortunately, this is the true color of the night sky. It may be too faint to be seen with your eyes, but the camera is sensitive enough to record it. Under urban or suburban skies, this color comes from light pollution. Under true dark skies, it comes from natural airglow.

To correctly record the color of a deep-sky object we need to remove this "near-sky" color from the Earth's atmosphere. Auto White Balance will sometimes work, but the best results are usually obtained by using a custom white balance set on the sky background itself. This is especially useful if we are shooting in-camera JPEGs. Our other option is to shoot raw and use Canon's Digital Photo Professional (DPP) software and use the eyedropper and "click white balance" in a blank area of the sky background.

Big and Little Dippers

The Big and Little Dippers are asterisms in the constellations of Ursa Major and Ursa Minor respectively. The two stars in the end of the bowl of the Big Dipper point to Polaris, the North Star, at the end of the handle of the Little Dipper.
This beginner astrophotograph was taken with a Canon EOS 60Da DSLR camera and Canon EF 16-35mm f/2.8L II USM zoom lens working at 16mm of focal length at f/2.8. A single 30 second exposure was made at ISO 1600 on a fixed tripod from a reasonably dark magnitude 6 observing site.

Iridium Satellite Flare

An Iridium satellite flares brightly in the constellation of Cygnus as clouds reflect light pollution. Mirror surfaces on the satellite reflect direct sunlight to cause the flare when the satellite is in sunshine high in Earth orbit while the ground is still shrouded in night.
This beginner astrophotograph was taken with a Canon EOS 60D DSLR camera and Canon EF 16-35mm f/2.8L II USM zoom lens working at 16mm of focal length at f/2.8. A single 30 second exposure was made at ISO 1600 on a fixed tripod from a reasonably dark magnitude 6 observing site.

Milky Way

The Milky Way, our own galaxy seen from the inside, runs diagonally across the frame through the Summer Triangle here, composed of the bright stars Vega at top left center, Deneb at bottom left and Altair at right.
The rich star clouds and dark nebulae of the Milky Way dominate the image. The Great Rift in the Milky Way runs through the star clouds in Aquila at upper right through Cygnus. Le Gentil 3, a large dark nebula, is at bottom left. The Northern Coalsack, another large dark nebula, lies to the right of Deneb and marks the beginning of the Great Rift.
The North America Nebula is a bright red hydrogen-alpha emission nebula just below Deneb. Another bright emission nebula, IC 1318, the Butterfly nebula, surrounds Sadr, Gamma Cygni, at the heart the Northern Cross.
This intermediate-level astrophotograph incorporates stacking several shorter exposures using software to equal a longer one. It was taken with a Canon EOS 60Da DSLR camera and Canon EF 16-35mm f/2.8L II USM zoom lens working at 16mm of focal length at f/2.8 on a fixed tripod. A series of 8-second exposures were made at ISO 6400 to minimize star trailing. It was taken from a reasonably dark magnitude 6 observing site.

Bright and Dark Nebulae

This dust choked region of the night sky is located in the constellations of Ophiuchus and Scorpius. The Pipe Nebula / Dark Horse at left is a large area of dark nebulosity, opaque dust and gas that hides stars behind it. Tendrils of dark nebulae stretch all the way across the frame to the Rho Ophiuchi complex at right. Antares, a red supergiant, is the brightest star in the image.
This advanced astrophoto image was shot with a Canon EOS 60Da DSLR camera and Canon 50mm f/1.4 USM lens working at f/4 with 54 minutes of total exposure through an IDAS LPS filter. Nine 6-minute exposures at ISO 800 were stacked with a min-max excluded average combination method. The white point was adjusted for correct color with a G2V color star calibration. A non-linear curve was applied to the linear raw data and the foreground sky color subtracted to give accurate color. The image was then contrast enhanced and color adjusted in post processing.

Rho Antares Nebula

The Antares – Rho Ophiuchi Region in Scorpius is one of the most beautiful and colorful areas of the entire night sky.
It contains dark nebulae where lanes of obscuring dust hide background stars, blue reflection nebulae where the dust is illuminated by the reflected light of nearby stars, and red emission nebulae where the hot hydrogen gas itself is glowing and emitting light.
Also visible is a rare orange/yellow reflection nebula around Antares, the brightest star at right center in the image. Antares is a red supergiant star with a radius about 1,500 times larger than the Sun, and is located about 604 light years distant.
Globular cluster M4 is just above and to the left of Antares. M4 is behind the nebulae complex in this image, at a distance of about 7,000 light years. M4 may be the closest globular cluster to our own sun. Shining at magnitude 5.6, it can be seen with the unaided eye under good conditions. At 26 arc minutes in size, M4 is nearly as large as the full moon, with a real diameter of about 55 light years. It is one of the most open and loose globular clusters, and would be astonishing if not obscured by thick clouds of obscuring interstellar dark matter in the region of Antares and Rho Ophiuchi.
Rho Ophiuchi is the triple-star surrounded by IC 4604, the large blue reflection nebula at the left of the photo. Emission nebula Sh2-9 is at top.
This advanced image was shot with a Canon EOS 60Da DSLR camera and Canon EF 200mm f/2.8L II USM lens working at f/2.8 with the lens riding piggyback on a telescope on an equatorial mount that was tracking the sky and auto-guided with a computerized CCD guide camera and off-axis guider. 30 minutes of total exposure from three 3-minute sub frames at ISO 800 and six 1-minute sub frames at ISO 1600 were shot through an Astronomik CLS with Canon RAW file format at a reasonably dark magnitude 6 observing site. A min-max excluded combine method was used to average the light frames and each was calibrated with a master dark made of x sub-darks and a master bias made from x sub-bias frames. A custom white balance from a G2V star was used. Image contrast and color were adjusted in post processing.

Hercules Globular Cluster

M13 is the Great Globular Cluster in the constellation of Hercules. It is one of the largest and most beautiful globular clusters visible from the northern hemisphere.
At magnitude 5.8, M13 is visible to the keen unaided eye at a dark-sky observing site. It is located about 25,000 light years away. It has an apparent angular diameter of 15 to 25 arc minutes, depending on the size of the telescope used to observe it. This corresponds to a real size of about 145 light years. It contains hundreds of thousands of stars.
This advanced Canon EOS 60D DSLR image is a stacked composite of six 6-minute exposures shot at ISO 800 through an apochromatic refractor with a focal length of 1,000mm at f/8. It was calibrated with a master dark frame made of 5 individual darks, and a master bias frame made from 4 individual bias frames. It was stacked with a min-max excluded average combine method. The white point was adjusted for correct color with a G2V color star calibration. A non-linear curve was applied to the linear raw data and the foreground sky color subtracted to give accurate color. The high-dynamic range image was constructed with a shorter exposure with masked highlights to preserve color and detail in the core of the cluster. A slightly blurred color enhancement layer was also added in post processing.

Trifid Nebula

M20, The Trifid Nebula, in the constellation of Sagittarius, is a remarkable object - large, bright and beautiful. It is a complex of red emission, blue reflection, and dark nebulae about the size of the full moon.
This advanced image was shot with a Canon EOS 60Da DSLR camera and an apochromatic refractor with a focal length of 1,000mm working at f/8 on an equatorial mount that was tracking the sky and auto-guided with a computerized CCD guide camera and off-axis guider. 16 minutes of total exposure from two 8-minute sub frames at ISO 800 were shot unfiltered as in-camera RAW images, at a reasonably dark magnitude 6 observing site. A min-max excluded combine method was used to average the light frames and each was calibrated with a master dark made of 5 sub-darks and a master bias made from 4 sub-bias frames. A custom white balance from a G2V star was used. Image contrast and color were adjusted in post processing.

Saturn

The spectacular beauty of the ringed planet Saturn was shot with a Canon EOS 60D DSLR camera using 640x480 movie crop mode at 60 frames per second with a 1/60th second exposure at ISO 6400 through a telescope with 11 inches of aperture and 5,600mm of focal length at f/20. The best 400 frames out of 3,600 total were selected and stacked in AutoStakkert!2 software and sharpened with wavelet sharpening in Registax. Individual color channels were registered and color adjusted in Photoshop CS5.

Focus

Astrophotography requires that you focus your camera on infinity, and this focus is critical. The high resolution of Canon's digital sensors require exact focus. In the old days of manual focus lenses, you could simply rack the lens to the hard stop at the infinity mark and be good to go. But today's modern autofocus lenses need to focus past infinity so the internal lens focus mechanism isn't damaged as the lens seeks focus and also to compensate for temperature-induced focus change at longer focal lengths and fast apertures. This means that you can't just use the infinity mark on the focus scale of the lens. And you definitely can't just turn the focus ring in the direction of infinity, until it stops.

The best way to focus on infinity is to use Live View and 10x magnification on a bright star or planet. The vari-angle LCD screen on Canon's latest DSLRs makes this easy, especially when the camera is pointed at a normally inconvenient angle, such as overhead when used at the bottom end of a long refracting telescope.

Here are a several important hints to remember when using Live View to focus:

Use the brightest star or planet in the sky to focus on. This is especially important the wider the angle of the lens that you use.

Set the lens to manual focus. Some of the longer, faster Canon lenses, such as the 200mm f/2.8 USM L II will autofocus on a bright star, but it is very difficult to get a star exactly on one of the small autofocus areas.

Manually set the focus scale to infinity to start. It is important to be at least close to focus to begin. If you are grossly out of focus, you won't see anything on Live View.

Turn on Live View exposure simulation in the menus (with most EOS Rebel models, this is always active when you're using Live View.)

Turn off Image Stabilization if the lens has this feature.

Set the camera to manual exposure mode.

Set the camera lens to its widest aperture.

Set the ISO to 1600 and the shutter speed to Bulb. This will ensure that you get the brightest Live View display.

Realize that Live View is not sensitive enough to show a faint nebula or galaxy, even through a telescope. All you will be able to see are the very brightest stars.

Aperture

Faster (wider) lens apertures and higher ISO speeds can mitigate the effects of trailing on a fixed tripod. Note however that photographing a star field is the single most difficult test of a lens. Every aberration will be revealed by the point sources of stars across the entire field. Many fast lenses need to be stopped two stops or more to get the best compromise between lens speed and optical quality. No lens is perfect, especially wide-open. Generally, the faster the lens, the more you will need to stop it down to correct aberrations. Some lenses, such as Canon's L series, can be used wide open, but test them for your specific requirements.

Exposure

The correct exposure for the night sky will be influenced by many different factors, but can be easily be determined by simply taking test shots and examining the results on the LCD on the back of the camera. The histogram is particularly helpful. The sky background will make up the bulk of the "mountain" of the histogram in an astrophoto, and the exposure should usually be long enough so that this "mountain" is completely separated from the left wall of the histogram box.

Note that the sky should not be black in your long-exposure astrophotos. It should have some tone. The sky is not black even at the darkest location on Earth. Once you are dark adapted, your eyes are sensitive enough to easily distinguish the sky from the horizon. If you underexpose to make the sky black, the faintest details in the subject will be difficult to separate from the noise in the image.

Exposure for an astrophoto is a compromise between image noise at high ISOs and long exposures, and dynamic range for holding detail and color in the brightest objects in the image. As you increase the exposure, the "mountain" of the histogram will move to the right. This normally means the image will have a higher signal-to-noise ratio, because longer exposures collect more photons which make up the signal in the image. But as you expose longer, you also saturate more stars and lose star colors and lose detail at the top end of the dynamic range. You also get more trailing on a fixed tripod with longer exposures.

Canon DSLRs have excellent noise characteristics. But if you are shooting long exposures under high ambient temperatures, the sensor is so sensitive it also starts recording electrons from heat in the camera. This will look like hot pixels and red, green and blue blobs of noise in the image. These are technically not noise, but rather a thermal signal. Luckily this thermal signal can easily be removed by using Long-Exposure Noise Reduction. This function takes a dark frame, an exposure as the same length as your light frame, but with the shutter closed, in the camera immediately after your light exposure has ended. Note that you will not be able to take another image until after this dark frame exposure has ended. After both the light frame and dark frame are taken, the camera subtracts the dark frame from the light frame to remove the thermal signal.

ISO

The best ISO setting for astronomical objects will also depend on many different factors. A good rule of thumb for longer tracked exposures is use a moderately high ISO, like ISO 800 or 1600 for faint nebulae and galaxies, and a low ISO for constellations, stars and star clusters. On a fixed tripod you may need to use a very high ISO if you want to minimize star trailing, but there are ways to improve the final image even at high ISOs, such as by using High-ISO Noise Reduction and more advanced techniques such as image stacking.

60D Histogram

The histogram for a test exposure image is a great way to determine the correct exposure for an astrophoto. The "mountain" of the histogram represents the sky background. Most astrophotos are correctly exposed when the mountain is at about 30 percent and fully separated from the left wall of the histogram box. This ensures that the critical faintest detail in the image is up out of the readout noise of the camera. At this exposure, multiple frames can be stacked to improve the signal-to-noise ratio in the final image. Longer exposures will reduce the dynamic range of the image by overexposing the stars in the image, causing loss of star colors.

Tips for Beginner Astrophotography

Start out simple – Learn how to focus on a star and how to determine the correct exposure by using the histogram. Here are some subjects you can shoot with just a camera on a tripod:

Twilight scenes with the crescent Moon with Earthshine and bright planets nearby like Venus or Jupiter

Asterisms like the Big and Little Dipper, and constellations like Cassiopeia and Orion

Satellite passes such as those by the International Space Station, and Iridium satellite flares

Circumpolar star trails

Meteors and meteor showers

The phases of the Moon

Aurora

Tips for Intermediate Astrophotography

Longer exposures are needed for fainter objects. This requires a motorized mount to track the sky as it turns due to the Earth's rotation. There are two basic mount types. One is an equatorial design that tracks the sky with the movement of one of its two axes. The other is an altazimuth design that tracks by moving both axes. You will be seriously limited in the length of exposures you can take with an altazimuth mounting because the field will rotate around its center due to the design of the mount. For serious long-exposure deep-sky astrophotography, you need an equatorial mount.

Longer focal lengths in the range of 300 to 3,000mm are also needed to shoot smaller objects. These can be Canon Super Telephotos or telescopes. There are several different telescope designs. Refractors use lenses; reflectors use mirrors; and compound designs, such as Schmidt-Cassegrains, use a combination of mirrors and lenses. Apochromatic refractors are usually an excellent choice for deep-sky astrophotography at focal lengths more than 600mm.

To hook your camera up to a telescope, you will need a 2-inch adapter to go into the back of the focuser on the scope, and a T-mount Canon adapter. The telescope takes the place of a camera lens.

One difference in nomenclature between telescopes and camera lenses is that telescopes are usually specified by their aperture, and camera lenses by their focal length. This is because telescopes usually work at a fixed aperture and focal ratio, and camera lenses have a variable aperture when they stop down to different focal ratios. A 300mm telescope means it has an aperture of 300mm. A 300mm camera lens means it has a focal length of 300mm.

The Canon 60Da Astrophotographic DSLR Camera

Canon's EOS 20Da was the first DSLR camera specifically designed for astrophotography. The 60Da carries on this tradition in a camera that has even more sensitivity and lower noise.

Sensors in DSLR cameras are more sensitive to deep red and infrared wavelengths than the eye, so ordinary digital SLRs use a long-wavelength filter to block most of these wavelengths to produce natural colors that more closely match the eye's spectral response.

Red nebulae emit most of their light at the hydrogen-alpha emission wavelength in the far red at 656.28 nanometers. The normal long-wavelength filter in a standard DSLR filters out much of this light.

Canon has modified the transmission of this filter in the 20Da and 60Da to pass more of the hydrogen-alpha wavelength to produce better pictures of red emission nebula. The 60Da filter transmits 3 times more hydrogen-alpha light than the regular 60D, and 1.5 times more than the 20Da. This makes the 60Da an excellent choice for astrophotography of the many beautiful red emission nebulae, which are also some of the largest objects in the night sky. M8, the Lagoon emission nebula shows a comparison between the 60D and 60Da hydrogen-alpha sensitivity. The pastel blue-green color in the 60D shot comes from Oxygen III emissions in the nebula which are not filtered by the long-wavelength filter.

This doesn't mean that you can't shoot emission nebulae with a normal Canon DSLR camera. You certainly can, but you will usually need a very dark sky and longer total exposures to do it. Special filters such as the Astronomik CLS will also help produce dramatically better images with a normal Canon DSLR. This comparison image shows the difference between the red North America emission nebula shot with a Canon 60D with and without a CLS filter. Astronomik even makes a CLS filter that snaps into Canon APS-C DSLR camera bodies in front of the mirror. This way the filter can be used not only with a telescope, but also with almost any Canon lens except the EF-S models.

Another exceptionally convenient feature of Canon's 60D and 60Da DSLRs is Vari-angle 3.0-inch Clear View LCD monitor. Frequently the camera will end up at an awkward angle at the bottom of a telescope that is pointing overhead. The vari-angle LCD screen can be tilted to make focusing, composition and exposure determination easy.

The Canon TC80-N3 Remote Interval Timer

For intermediate astrophotography we will frequently be taking many long exposures and averaging them together. Canon's TC80-N3 is an indispensable tool for this. It is a remote release that incorporates an intervalometer.

It can be programmed for a delay before the first frame is taken, and then for any number of frames at any exposure, with a user-specified pause between frames if desired.

Note that the camera must be set to Bulb exposure to use the TC80-N3 for exposures longer than 30 seconds. The shooter then can program in a specific length of time on the remote controller’s LCD panel for the shutter to stay open, ranging up to many hours. An adapter supplied with the 60Da must be used with the TC80-N3 to convert the Canon N3 proprietary plug to a single-pin E3 plug, so it can be used with the EOS 60Da.

See Canon's excellent quick guide to the TC80-N3 for more information and tips on usage.

Telescope setup

A wide-angle lens is piggybacked with a ball-and-socket head on top of a telescope on an equatorial mounting in this equipment setup for intermediate astrophotography. The equatorial mounting tracks the sky to compensate for the Earth's rotation, allowing for long exposures without star trailing. A 2-inch T-mount adapter mates a second camera to a refracting telescope with 1,040mm of focal length at f/8. In this case, the camera's lens is removed and the telescope acts as the camera lens. An anti-dewer heating element is wrapped around the telescope to prevent dew from forming on the objective.

EOS 60Da vs. EOS 60D

The relative hydrogen-alpha sensitivity of the Canon EOS 60D (left) and 60Da (right) can be compared in these images of M8, the Lagoon Nebula. The 60Da has a specially modified long-wavelength filter that transmits 3 times more hydrogen-alpha light than the standard filter in the 60D. This makes astrophotography of red hydrogen-alpha emission nebulae easier with the 60Da. The more pastel shades of cyan dominate the 60D image are from Oxygen III emissions in the nebula.

EOS 60Da image filtered and unfiltered

Although the standard Canon EOS 60D DSLR camera has a long-wavelength filter that does not transmit as much hydrogen-alpha light as a 60Da, it is still possible to shoot red emission nebulae with the 60D. A reasonably dark location and a special filter, in this case the Astronomik CLS filter, can be used with longer exposures to produce good results with brighter hydrogen-alpha emission nebulae. The North America Nebula was shot unfiltered (left) and with the CLS filter (right).

Dealing with Dew

When you are out shooting astrophotos, you will very probably run into problems with your lenses dewing up when the temperature drops at night (unless you are shooting in the desert).

The best way to combat dew is to prevent it from forming by applying a small amount of heat to your lens. This is best done by using an anti-dewer. This is a heated strip of material that you wrap around your lens that is powered by a 12-volt battery. You can purchase these from DewNot or Kendricks.

Shooting Tips

Go someplace dark to shoot! Get as far away from light pollution as possible – this means driving well out into the country!

Use a red flashlight. After a half-hour or so in the dark, your eyes will become dark adapted and you will be able to see surprisingly well. A red light that is not too bright will help preserve your dark adaptation.

Use a light fog filter to bring out bright stars in constellation shots.

Tape down the focus and zoom rings after achieving infinity focus.

Refocus if you change the focal length on a zoom lens, as many zooms are not parfocal.

Turn down in-camera sharpening all the way, it will exaggerate noise at high ISOs and long exposure times.

Set a custom white balance on sky background.

At high ambient temps use in-camera long-exposure noise reduction.

Shoot JPEG and Raw concurrently (RAW + JPEG). This is helpful, as you can approximate what images will look like with a non-linear curve applied to the linear data, particularly if you plan to process the RAW photos in a specialty astronomical image processing program which treats the images are linear raw files (which appear extremely dark, low contrast, and not color-corrected).

Turn off the image display on the LCD monitor after each shot; it will heat the camera up and increase the thermal signal/noise.

Carry extra camera batteries, or use a 12-volt adapter and 12-volt deep-cycle battery – it can also power your anti-dewers.

Look up and observe. Enjoy the beauty and wonder of the night sky! It is awe inspiring to stand out under a dark sky far from today's man-made light pollution and realize photons of light from these objects travel incredible distances across the universe and interact with our own eyes and consciousness. And best of all, we can record these photons for posterity with our Canon DSLR cameras!

Safety Tips

If you are going out observing at a remote location, let someone know where you are going and when you plan to be back. Your cell phone might not work and they will know to come looking for you if you have car trouble.

Be aware of any potential hazards from wild animals and humans at your observing site. The general rule of thumb, in both cases, is that if you don't mess with them, they won't mess with you. However, if you are in bear country, observe common sense rules such as not leaving any food out. It may make sense to have a portable, battery-powered radio playing, allowing animals like bears will hear you before they see you, so they won't be startled by your presence.

In mosquito and tick-prone areas, use an insect repellant with DEET. It is the only scientifically proven insect repellant. This is important because of illnesses like the mosquito-borne West Nile Virus and tick-borne Lyme disease.

Resources

Utilizing the EOS 60Da or any of Canon's digital SLR cameras and some of the basic tips and techniques discussed above is a great way to begin capturing the vast universe that we live in. Below is a list of resources to help plan out the best times and locations for the best chances of a successful shoot.

SpaceWeather - Find out what's happening on the Sun and the chances of seeing an aurora.

FREE DOWNLOAD: Check out our PDF quick reference guide "DSLR Camera Settings for Astrophotography", in the Resources tab below. This is an ideal field guide for EOS shooters looking to get started in astrophotography.

The CDLC contributors are compensated spokespersons and actual users of the Canon products that they promote.

Big and Little Dippers

The Big and Little Dippers are asterisms in the constellations of Ursa Major and Ursa Minor respectively. The two stars in the end of the bowl of the Big Dipper point to Polaris, the North Star, at the end of the handle of the Little Dipper.
This beginner astrophotograph was taken with a Canon EOS 60Da DSLR camera and Canon EF 16-35mm f/2.8L II USM zoom lens working at 16mm of focal length at f/2.8. A single 30 second exposure was made at ISO 1600 on a fixed tripod from a reasonably dark magnitude 6 observing site.

Iridium Satellite Flare

An Iridium satellite flares brightly in the constellation of Cygnus as clouds reflect light pollution. Mirror surfaces on the satellite reflect direct sunlight to cause the flare when the satellite is in sunshine high in Earth orbit while the ground is still shrouded in night.
This beginner astrophotograph was taken with a Canon EOS 60D DSLR camera and Canon EF 16-35mm f/2.8L II USM zoom lens working at 16mm of focal length at f/2.8. A single 30 second exposure was made at ISO 1600 on a fixed tripod from a reasonably dark magnitude 6 observing site.

Milky Way

The Milky Way, our own galaxy seen from the inside, runs diagonally across the frame through the Summer Triangle here, composed of the bright stars Vega at top left center, Deneb at bottom left and Altair at right.
The rich star clouds and dark nebulae of the Milky Way dominate the image. The Great Rift in the Milky Way runs through the star clouds in Aquila at upper right through Cygnus. Le Gentil 3, a large dark nebula, is at bottom left. The Northern Coalsack, another large dark nebula, lies to the right of Deneb and marks the beginning of the Great Rift.
The North America Nebula is a bright red hydrogen-alpha emission nebula just below Deneb. Another bright emission nebula, IC 1318, the Butterfly nebula, surrounds Sadr, Gamma Cygni, at the heart the Northern Cross.
This intermediate-level astrophotograph incorporates stacking several shorter exposures using software to equal a longer one. It was taken with a Canon EOS 60Da DSLR camera and Canon EF 16-35mm f/2.8L II USM zoom lens working at 16mm of focal length at f/2.8 on a fixed tripod. A series of 8-second exposures were made at ISO 6400 to minimize star trailing. It was taken from a reasonably dark magnitude 6 observing site.

Bright and Dark Nebulae

This dust choked region of the night sky is located in the constellations of Ophiuchus and Scorpius. The Pipe Nebula / Dark Horse at left is a large area of dark nebulosity, opaque dust and gas that hides stars behind it. Tendrils of dark nebulae stretch all the way across the frame to the Rho Ophiuchi complex at right. Antares, a red supergiant, is the brightest star in the image.
This advanced astrophoto image was shot with a Canon EOS 60Da DSLR camera and Canon 50mm f/1.4 USM lens working at f/4 with 54 minutes of total exposure through an IDAS LPS filter. Nine 6-minute exposures at ISO 800 were stacked with a min-max excluded average combination method. The white point was adjusted for correct color with a G2V color star calibration. A non-linear curve was applied to the linear raw data and the foreground sky color subtracted to give accurate color. The image was then contrast enhanced and color adjusted in post processing.

Rho Antares Nebula

The Antares – Rho Ophiuchi Region in Scorpius is one of the most beautiful and colorful areas of the entire night sky.
It contains dark nebulae where lanes of obscuring dust hide background stars, blue reflection nebulae where the dust is illuminated by the reflected light of nearby stars, and red emission nebulae where the hot hydrogen gas itself is glowing and emitting light.
Also visible is a rare orange/yellow reflection nebula around Antares, the brightest star at right center in the image. Antares is a red supergiant star with a radius about 1,500 times larger than the Sun, and is located about 604 light years distant.
Globular cluster M4 is just above and to the left of Antares. M4 is behind the nebulae complex in this image, at a distance of about 7,000 light years. M4 may be the closest globular cluster to our own sun. Shining at magnitude 5.6, it can be seen with the unaided eye under good conditions. At 26 arc minutes in size, M4 is nearly as large as the full moon, with a real diameter of about 55 light years. It is one of the most open and loose globular clusters, and would be astonishing if not obscured by thick clouds of obscuring interstellar dark matter in the region of Antares and Rho Ophiuchi.
Rho Ophiuchi is the triple-star surrounded by IC 4604, the large blue reflection nebula at the left of the photo. Emission nebula Sh2-9 is at top.
This advanced image was shot with a Canon EOS 60Da DSLR camera and Canon EF 200mm f/2.8L II USM lens working at f/2.8 with the lens riding piggyback on a telescope on an equatorial mount that was tracking the sky and auto-guided with a computerized CCD guide camera and off-axis guider. 30 minutes of total exposure from three 3-minute sub frames at ISO 800 and six 1-minute sub frames at ISO 1600 were shot through an Astronomik CLS with Canon RAW file format at a reasonably dark magnitude 6 observing site. A min-max excluded combine method was used to average the light frames and each was calibrated with a master dark made of x sub-darks and a master bias made from x sub-bias frames. A custom white balance from a G2V star was used. Image contrast and color were adjusted in post processing.

Hercules Globular Cluster

M13 is the Great Globular Cluster in the constellation of Hercules. It is one of the largest and most beautiful globular clusters visible from the northern hemisphere.
At magnitude 5.8, M13 is visible to the keen unaided eye at a dark-sky observing site. It is located about 25,000 light years away. It has an apparent angular diameter of 15 to 25 arc minutes, depending on the size of the telescope used to observe it. This corresponds to a real size of about 145 light years. It contains hundreds of thousands of stars.
This advanced Canon EOS 60D DSLR image is a stacked composite of six 6-minute exposures shot at ISO 800 through an apochromatic refractor with a focal length of 1,000mm at f/8. It was calibrated with a master dark frame made of 5 individual darks, and a master bias frame made from 4 individual bias frames. It was stacked with a min-max excluded average combine method. The white point was adjusted for correct color with a G2V color star calibration. A non-linear curve was applied to the linear raw data and the foreground sky color subtracted to give accurate color. The high-dynamic range image was constructed with a shorter exposure with masked highlights to preserve color and detail in the core of the cluster. A slightly blurred color enhancement layer was also added in post processing.

Trifid Nebula

M20, The Trifid Nebula, in the constellation of Sagittarius, is a remarkable object - large, bright and beautiful. It is a complex of red emission, blue reflection, and dark nebulae about the size of the full moon.
This advanced image was shot with a Canon EOS 60Da DSLR camera and an apochromatic refractor with a focal length of 1,000mm working at f/8 on an equatorial mount that was tracking the sky and auto-guided with a computerized CCD guide camera and off-axis guider. 16 minutes of total exposure from two 8-minute sub frames at ISO 800 were shot unfiltered as in-camera RAW images, at a reasonably dark magnitude 6 observing site. A min-max excluded combine method was used to average the light frames and each was calibrated with a master dark made of 5 sub-darks and a master bias made from 4 sub-bias frames. A custom white balance from a G2V star was used. Image contrast and color were adjusted in post processing.

Saturn

The spectacular beauty of the ringed planet Saturn was shot with a Canon EOS 60D DSLR camera using 640x480 movie crop mode at 60 frames per second with a 1/60th second exposure at ISO 6400 through a telescope with 11 inches of aperture and 5,600mm of focal length at f/20. The best 400 frames out of 3,600 total were selected and stacked in AutoStakkert!2 software and sharpened with wavelet sharpening in Registax. Individual color channels were registered and color adjusted in Photoshop CS5.

60D Histogram

The histogram for a test exposure image is a great way to determine the correct exposure for an astrophoto. The "mountain" of the histogram represents the sky background. Most astrophotos are correctly exposed when the mountain is at about 30 percent and fully separated from the left wall of the histogram box. This ensures that the critical faintest detail in the image is up out of the readout noise of the camera. At this exposure, multiple frames can be stacked to improve the signal-to-noise ratio in the final image. Longer exposures will reduce the dynamic range of the image by overexposing the stars in the image, causing loss of star colors.

Telescope setup

A wide-angle lens is piggybacked with a ball-and-socket head on top of a telescope on an equatorial mounting in this equipment setup for intermediate astrophotography. The equatorial mounting tracks the sky to compensate for the Earth's rotation, allowing for long exposures without star trailing. A 2-inch T-mount adapter mates a second camera to a refracting telescope with 1,040mm of focal length at f/8. In this case, the camera's lens is removed and the telescope acts as the camera lens. An anti-dewer heating element is wrapped around the telescope to prevent dew from forming on the objective.

EOS 60Da vs. EOS 60D

The relative hydrogen-alpha sensitivity of the Canon EOS 60D (left) and 60Da (right) can be compared in these images of M8, the Lagoon Nebula. The 60Da has a specially modified long-wavelength filter that transmits 3 times more hydrogen-alpha light than the standard filter in the 60D. This makes astrophotography of red hydrogen-alpha emission nebulae easier with the 60Da. The more pastel shades of cyan dominate the 60D image are from Oxygen III emissions in the nebula.

EOS 60Da image filtered and unfiltered

Although the standard Canon EOS 60D DSLR camera has a long-wavelength filter that does not transmit as much hydrogen-alpha light as a 60Da, it is still possible to shoot red emission nebulae with the 60D. A reasonably dark location and a special filter, in this case the Astronomik CLS filter, can be used with longer exposures to produce good results with brighter hydrogen-alpha emission nebulae. The North America Nebula was shot unfiltered (left) and with the CLS filter (right).

DSLR Camera Settings for Astrophotography The quick reference guide by Jerry Lodriguss is an ideal field companion to this article on astrophotography techniques with the EOS system.